Tektronix FG501 User manual

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070-1431-01
Te
k tro nb
c
CO M M ITT E D TO E XC
E LLE N C E
FUNCTION
GENERATOR
1
INSTRUCTION
M ANUAL
Te k
tro n i x , Inc .
Ρ .
Ο . Box
500
B eaverto n , Orego n
97077

Serial N u m
ber
F irst p ri n ti ng
A ug u st Ι 972

nearest Tektron
timber
r
is warranted against detecfit "c meAc' - iw .i and
rmal use,
for a
nix will repair or replace, at its op
termined to
be
defecUve
within the wana
ix Servicx? !^ ι
;υ
,
vvorkt
iniflal shipment,
produccis de
avd rv-
?
urnpd, freight
prepaid ., to
fitness wof I 01i Y

V%

k1i
Please direct
all requests for service or replacement parts to the
nter or Field Office, include the type or
product and its serial number .
Copyright -) 197 2 , 1978 by Tektronix .
reserved . Contents of this publication may not be
duced in any form without the permissio
ektronix, I
Products of Tektronix, inc . and its subsidiaries ar ; a
covered by U .S . and foreign patents and/or pending
patents .
TEKTRONIX, TEK, SCOPE-MOBILE, TELEQWPMENT,
and

are
registered
trademarks of Tektronix, Inc .
Printed
in U .S .A . Specification and price change
privNeges are reserved .

TABLE Ο F CO N T EN TS
S
E CTIO N 1
S
E CTIO N 2
W A RN ING ,
THE
FO LL
O
W I NG S ERV ICI N G I N ST RU CTIO N S AR EF OR U SE BY
Q
U
A L I F I E D PER-
SO
NNEL O NL Y . T O AV OID PER SO N A L I NJUR
Y,
DO NOT
PERFO RM ANY S ERV ICI N G
OT HER THAN THAT CO N TAI NE D IN OPER ATI NG
I N
ST
RU CTIO N S UNLE SS YO U A RE
QUA L I F I ED TO DO SO .
C HA N G E I NF O RM ATIO N
SE CTIO N 3 AD JUST
MEN T
3-1
SE CTIO N 4 M AI NT EN A N C
E AND I NT ERF ACI NG I NF O RM ATION 4-1
SE CTIO N 5 CI
R
CU
IT D E
SC
R I P TIO N
5-1
SE
CTIO N 6 O P TIO N S
6-1
SE CTIO N 7 REPL AC E A BLE ELE CT
R ICA L P A R TS 7-1
S E CTIO N 8 DIAG RA M A ND CI
R CU IT B
OA
RD I LLU ST R ATIO N 8-1
SE CTIO
N9 REPL AC E A BLE ME CHAN ICA L P A R TS A
N D E X PL
OD
E D V IE W 9-1
,. P age
O PER ATI N G I N ST RU CTIO N S
1-1
S PE CI F ICATIO N AND PERF O RM
ANC E C HE C K 2-1

Fig . 1-1 . FG 501 Function
Generator

I N T
R OD U CTIO N
Th e F G 501 Function
Generator is designed to op erate
i nα TM 500-Series p ower mo d ule
.
L
ow d istortion si n e,
s q uare, triangle, pulse, an d ramp
waveformsfrom 0 .001 Hz
to 1 MH z as well as α +2,5 volt sq uare-wave
trigger are
available at t he front p an el . V ariable DC
offset of
±7
.5 volts
is also p rovide d . Α "h ol d " feature allows
t he ge n erator
outp
ut to be abru p tly h alted at its instantaneous
voltage
level an d h el d t here un
til ma n ually switc h ed on again .
Α voltage-controlle d fre q uency (V C F) in p
ut is provi d ed
to control t h e out p ut fre quency from
an exter
n
al voltage
source . T he outp ut fre quency can be swe p t above
or
below t h e selecte d fre q ue ncy to α maxim u m of 1000 :1
de pe nd ing on t he polarity and am p litu d e of t he V C F i n put
an d t h e selecte
d output frequency .
Also inclu d ed is
an exter n al gate in p ut t h at allows t he
generator to be
tur n ed on for t h e d uration of an externally
ap p lie d gating
signal . T h is mo d e p rovi des eit h er α
single
cycle outp ut or α train
(burst) of p reselected waveforms
dependi n g on t he gating sig
n al width an d t he ge n erator
fre q
uency setti n g . T he p h ase (start level)
of t he waveform
burst
can be varie d ±90° b yα fro n t- p an
el con trol .
T he variety
of swe p t a n d mo d ulate d signals
available
from t he F G 501 ma ke
it es p ecially usef u l for suc
h
ap p
lications as testing
servo-system or amplifier
res p onse, distortio n , and stability ;
FM ge n eratio n an d
fre q
uency multiplicatio n ; or sim p ly u
sed as α variable
beat-fre q ue ncy
oscillator, re p etitio n -rate,
o r tone-burst
ge n erator . T h e
sq uare-wave trigger outp ut
ca
n
be use d as
α source for tra n
sistor-tra n sistor logic (TT L ) or
to syn-
ch ro n ize an exter n al
device such as an oscilloscope
or
counter .
T h
e F G 501 is calibrated a nd ready for use w h en
received
. It is design ed to op erate in any compartment of α
TM 500-Series
power module only . R efer to t he p ower
mo d ule I n st r uctio n
Manual for line voltage re q ui r eme n ts
a nd power mo d ule operatio n .
REV . C JUL 197 8
OPERATING
I N
ST
RU CTIO N S
Installation an dR emoval
Sectio n 1- F G 501
Turn t he p ower mo d ule
off before inserting t h e plug-
in ; otherwise, d amage
may occu r to t h e plug-in
c
ί
rcuitry . B ecause of t h ehigh cu
r rent drawn by t he
FG 501, it is also r ecommen d
e d th at t he p owe r
mo
d ule be turned off before
removing t h e FG 501 .
R efer to
Fig . 1-2 . C h ec k to see th
at t he plastic
barriers on t h e
interconnecting jac k of t h e
selecte d
p ower module compa r
tment matc h th e cut-outs
in
t he F G 501 circuit board edge
connector .
Align t h e F G 501 ch assis wit h t he upper a nd
lower
guides of t h e selected com p artme n t . P ush t h e mo d ule in
a nd p ress firmly to seat t he circuit board in t he inter-
connecting j ac k .
Pull t he P ower switc h
on t h e fro n t p anel of t he p ower
module to apply p ower to t h e F G 501 .
Observe t
h
at t h e
P O WER indicator lig h t on t he F G 501 comes
on .
R emove t he F G 501 from t he power
mo d ule by p ulli ng
t he release latc h at t he bottom of t he fro n t pa n el a
nd
sliding
t he unit straig h t out of t he p ower module .
F ig . 1-2 . P l u g-i n i n stallatio na nd r emoval .

O p e
r ating I n st ru ctions-
F
G
501
O PER
ATI N G CON
SID ER ATIO N S
ΝΟΤΕ
Befo
r
e
using t h e FG 501
fo r t h e first
time, r ead t he
Operati n g Co n
siderations in t h is section
an d t he
d
esc r i p tion of t he f r
ont-panel controls,
connectors,
and
indicators i n F
ig . 1-3 .
Out p ut Con
n ections
T he
output of t he F G 501 is designed to operate
as α
voltage source in series
wit h 50 Ω and wor k i ng i n to
α50 Ω
load . At t h e
h
ig
h
er
f r e qu encies, an un te r mi n
ated or
im p roperly
termi n ated output will ca u se
excessive
a b erratio n s on t he outp ut waveform
(see Impe d ance
M atc hing disc u ssion) .
L
oa
d s less than 50 Ω will re d ucet he
waveform am p litude .
E xcessive
distortion or a b errations due
to imp r op er
terminatio n is less li k ely to occur at
t he lower fre q ue n cies
(especially wit h sine an d tria n gle waveforms)
. H oweve r , to
en sure t h at waveform pu r ity is
preserve d , observe t he
following precautio
ns :
1 . U se q
uality 50 Ω coaxial cables and
con n ectors .
2
.

M
a
k e all con n ectio n s tig h t a nd as s
h ort
as p
ossible .
3 . Use q
uality atte nu ators, if necessa
r y, to red u ce
waveform am p litude to
sensitive ci r cuits .
4 . U se termi n ators or
im p edance-matc h i n g
devices to
avoid reflectio n s w
h
e
n usi ng long ca b les, i .e .,
six feet or
more .
5 . E nsure t h at atte n uators,
termi n ations, etc . h ave
ad e qu ate power- h
andli ng capa b ilities for t he output
waveform (a pp
roximately 0 .5 W into α 50
Ω load) .
P ower o
u tput is determine d by t he selecte
d waveform,
its am
p litude, a nd t h e amou n t of
offset voltage selected .
T he p h ysical a nd electrical ch
aracteristics of t he pu lse-
tra n smitti n g cable d
etermi ne t h e ch aracteristic
im-
pedance, velocity of
prop agatio n , and amou n t of
sig n al
loss . Signal loss,
d ue to en ergy d issipatio n
i nth e ca b le
dielectric,
is p ro p o r tio n al to t h e fre q ue
n
cy ;
t h erefore, α
few feet
of ca b le can atte n uate h ig h -freque ncy
i n forma-
tio n in α
fEkst-rise p ulse . It is importantto
k
eept
h ese cables
as sh
ort as possible .
Wh en signal com
p arison measurements
or time
difference determinatio
ns are made, t h e
two signals from
t he test device s
h
o
u ld travel t h roug h
coaxial cables wit h
identical loss
and time-d elay c h
aracteristics .
If t here is α d o voltageacross
t h eoutput load, t h e
output
p ulse
am p litu d e will be
compressed ; or in some
cases, if
t he voltage excee d s
±10 V, it may sh ort t
heoutput . To
preven t t h is from
occurring, t h e output
must b e coupled
t h roug hα do
b loc king cap acitor to
t h e loa d . The time
con sta n t of
t he cou p li n g ca p acitor an d
loa d must be lo n g
eno ug h to
maintai n p ulse flat ness .
R isetime and Falltime
If t h e out p ut pulse
from t h e F G 501 is use
d for
measuri ng t he r ise or
falltime of α d evice, t
h e risetime
ch aracteristics of
associate d eq ui p me
n t may h ave to be
considered . If
t he risetime of t he device un
der test is at
least 10 times
greater t han t he combine
d risetimes of t he
F G 501 plus
t he monitoring oscilloscope
a nd associate d
cables,
t h e error i n troduced will
n
ot
exceed 1 ο/ο an d
generally
can be ignored . If t he rise
or falltime of t he test
device, h owever, is less
t han 10 times as long as
t he
combi ned risetimes of
t h e testi ng system,
t h e actual
risetime of t he device
will h ave to b e d
eterminedfrom t h e
risetime of
eac h compone n t ma k i ng up
t h e system . T h is
equals t he s q uare
root of t he sum of
t he sq uares of t h e
i n divi d ual
risetimes . Co n versely,t
herisetimeoft h edevice
under test can be found
from t h e same relations
h ip if all
t he actual risetimes in t
h e system are kn own except
t h at of
t he device under
test .
Im p edance
M atc h i ng
R eflectio n s . As α pu
lse travels d own α tra
nsmission
line, eac h time it encou
n ters α mismatc
h ,
or an im p
eda n ce
differe n t t han t
he transmission li
n e, α r eflection is
generate da
nd sent backalon g t he
line to t he source . T he
amplitude
and p olarity of t he reflectio
ns are d etermi
n
ed
b y t he
amount of t h e encountere
d impedance i n
relatio n
to t he ch
aracteristic im p
edance of t he ca b le .
If t he
mismatc
h im p edance is h ig h er t
han t h e line, t h e
reflectio n
will be of
t h e same p olarity as
t h e applied sig
n al ; if it is
lower, t h e reflection
will b e of o p posite p ola r ity .
If t h e
reflecte d signal retur ns before
t h e pulse is en d ed,
it ad ds
to or
subtracts from
t h e am p lit u de of t
hepulse . Th is
distorts t he p
ulse s h ape a nd
amplitude .
M atc h ing N etwor ks . T
he following d escribes
met h ods
for
matc h ing impedance
networ k s i n to
relatively
low
impedances . If t h e F G
501 is d rivi ng α h ig
h impe d ance,
suc h as t he 1 ΜΩ
i np ut impedance of t
h
e
vertical inpu t for
an oscilloscope,
t h e transmissio n line
must be termi n ate d
REV . Β JUL 197 8

Selects sine, triangle,
square, ramp, and pulse
output waveforms . Pulse
and ramp waveform
duration is 1/2f . See
Operating
Con-
siderations for addi-
tional information .
Concentric with OFF-
SET control . Varies am-
plitude
of waveform at
the OUTPUT connector
from less than 500 mV
(fully ccw) to 20 V p-p
open circuit ( S N
B130000-up) . For SN
below 8130000, con-
trol
is label OUTPUT and
provides a maximum
of
15 V p-p open
circuit .
REV C,
MAR 197 9
FUNCTION Selector
AMPL Control
OFFSET Control
Concentric with AMPL
contrN . For S N
13130000-up,
control
pullout provides a
var-
able dc offset
voltage
from zero (centered) to
either -- 7 .5 V (fully cew)
or

+7 .5 V (fully cw) .
When pushed in pro-
vides zero off-set, For S N
below B130000 control
does not pull out and
offset limits are - 5 V to
+5 V .
PHASE Control
When pulled out provides
continuously variable
selection of the gated
output waveform start
level (phase) from +90 0
(fully ccw) to -90 0 (fully
cw) referenced to the sine
or triangle waveform 0 0
starting point . Used in
conjunction with the
GATE INPUT connector
when operating in gated
output (burst) mode .
TRIG
OUTPUT
Connector
Bs m connector
that pre
vides a +2 .5 V square-
wave trigger output into
a
600 0 load,
OUTPUT Connector
Bnc connector that pro-
vides the output wave-
form selected by the
FUNCTION selector,
POWER Indicator
GATE INPUT Connector
A brie
connector for
applying a +2 V
to +15 V
gating signal to the
generator .
Fig . 1-3 . Operating controls and connectors .
when power is ap-
the
FG 501 .
Operating Instructions-FG 501
FREQUENCY Hz Dial
The frequency of sine,
triangle and square
waveforms is the
dial
reading times
multiplier .
Ramp arid pulse
wave-
forms have a
frequency
approximately 1 .6X
dial
setting times
multiplier
with the MULTIPLIER
at
1 or above and
a fre-
quency of approximately
2X dial setting on the
three lowest ranges of
the
MULTIPLIER selec-
tor .
Provides vernier selec-
tion of output frequency
from the fully cow
(calibrated) position to
approximately 0 .35% of
full scale in the fully ccw
position .
MULTIPLIER Selector
Selects frequency range
in 9 decade steps and
provides three "hold"
positions (between the
lowest three multiplier
positions) that hold the
generator output at any
desired
instantaneous
voltage level .
Bnc connector for apply-
ing an external voltage
for controlling
the output
frequency o f the
generator . A 10 V input
provides a frequency
range of 1000 : 1 .
1431-13A

O perating
Instructions-FG 501
into α 50 Ω attenuator
and α 50 Ω termination
at the
oscilloscope input .
The attenuator isolates
the input
capacity of the device
. Distortion can be
caused by this
input
capacity .
Α simple
resistive impedance-matching
n etwork t hat
p rovides
minimum attenuation is
illustrated in F ig . 1-4 . To
match impedance with t he
illustrated network, the follow-
i n g co n ditio ns must exist
:
and
Th
erefore :
(R, +
Ζτ ) R
τ
m
u st eq ual Ζ ,
R ,+
Ζτ
+ R z
R, +

Z,
R 2

must equal Ζτ
Z,+ R z
R
ι R z = ΖιΖ
z
;
and R ιΖι =
R
z ( Ζτ - Ζ I )
or R ι =

Ζτ
( Ζτ - Ζι )
and
R
z = Ζι -
\
Ι

Ζ 2
Ζ
_
τ
Ζ ,
F or exam p le ; to matc
hα50 Ω system to α 125
Ω system,
Ζ , eq uals 50
Ω a n d Ζ
2
eq uals 125 Ω .
Th erefore :
R,=-\/i25-(125-50) =96 .80
an dR 2 =
50

125
25
50
-
64
.6 Ω
Wh en
co n structi n g suc h α d
evice, t h e environme n t
surrounding
t h e compo nents s h ould also
b e design ed to
provide α
transition b etwee n t he im p
edan ces . K eep in
mind t h at t
h
e
c h a r acteristic im p eda n ce of
α coaxial d evice
is determined
by t he ratio b etwee n t
h e outsi de diameter of
t
h
e
in ne r conductor to t
h
e i
n si de d iameter of t he
outer
cond uctor . τ ο = 138/
ε log,o D/d, w here D is t
h
e
i n side
diameter of t h e outer
con d uctor, a n d d is
t he outside
diameter of t
he in ne r conductor . ε is
t h e dielectric co n s-
tant (1 in air) .
Attenuation R atios . Th o u g
h t he networ k i n F ig .
1-4
provi
d es mi n imum atte n
uatio n fo r αpu r ely
resistive
im pe d a n ce-matc h i n g
d evice, t h e atte nu atio nas seen
from
o ne end does
not eq ual t h at see n from
t he ot he r en d . Α
signal ( Ε ,)
ap p lied from t h e lower impeda
n ce sou r ce ( Ζ ,)
en cou n ters α
voltage atte n uation ( Αι )
w h ic h is g r eater
t han 1 an d less
t han 2, as follows :
Α , =Ez =
Ζτ
+ 1
Fig . 1-4
. I mp edance-match
i ng n etwor kth at pr ovi d es
m i n im um
attenuatio n .
Α sig n al (
Ε
2)
app lied from
t he h ig h er im ped
an ce source
( Ζ
2)
en cou
n ters α greater
voltage atten
u atio n ( Α
2)
wh ic
h
is
greater t
han 1 a nd
less t h an 2 (Z2/Z,) :
_ Ετ __
R'
+
R'

+ 1
Az =

Ε
ι

Rz

_EL
In t h e
example of matc
hing 50 Ω to
125 Ω .
Α '

925
+1=1 .77
Α 2 =
96
.8 + 96 .8
+
1 = 4 .44
64 .6
50
T
he illustrated
n etwor k can b
e mo d ified to p
rovide
different attenuatio
n ratios by
ad d i ng anot
h er resistor
(less t han R,)
betwee n Ζ , an d
t h e j un ctio n of
R, an dR z .
Duratio n of R
amps and P ulses
Th ed
uration of ramp
an d p u lse
waveforms is always
eq
ual to t he h alf-cycle
time of t h e
sine, square, or triangle
waveform freque
n cy . For MUL
TI PL I ER setti n gs of
1 or
greater, t
he retrace/off time is suc
h t h at t h e
waveform h as
αdu ty cycle
of approximately 80
ο / ο, i .e ., fre quen
cy equals
a pp roximately
1 .6 Χ FRE Q
UEN CY Hz
dial setti n g . For
MUL TI PL
I ER setti n gs less
t h an 1, t h e
retrace/off time is
from
10 ms to 100 ms,
w h ic h results
i n duty cycles
a
pproaching 100 ο/ο ;i
.e ., frequency equals
approximately
2 Χ FRE Q UEN CY Hz
d ial setting .
REV .
Β JUL
197 8

Free- R u nn
ing
O
u tput
T he
following proced u re provi d es α fr ee-run n ing
waveform outp ut
wit h variable fre q ue n cy an d amplitude .
1 . Set t h e A MPL control to t he fully co u ntercloc k wise
p osition and t he O FF S E T co n trol to t he 0 (cen
tered)
positio n . C h eck t h at t he PH AS E co
n tr
ol is
pus h ed in (off) .
2 . Set t
he
FUN
CTIO N selector to t h ed esired
waveform
(see F ig . 1-5) .
F ig . 1-5 .
O
u t p ut wavefo r ms availa b le f r om t he F G 501 .
3 . Select t he desire d fre quen cy
wit h t h e MUL TI PL I ER
selector a nd FRE Q UEN CY Hz d ial
. F
or
exam p le, if t h e
MUL TI PL I ER selecto r is set to t
he10 5 p osition an d t h e
FRE Q UEN CY Hz d ial is
at 5, out p ut fre q ue ncy is 500 kH z ;
i .e ., MUL TI PL I ER
setting Χ FRE
Q
UEN CY Hz setti ng . T h e
output fre q ue
n
cy is
calibrated w h e n t h e FRE Q UEN CY
VERN
I
ER
control is in t h e fully cloc k wise p ositio n . T h e
d uratio n of ram
p
a
n
dpulse
waveforms is depende n t on t he
MUL
TI PL I ER setti n g . See Duration of R am p s an d
P
ulses
under O p erating Co n si d eratio n s for furt h er
i n formatio n .
4 . Connect t h e loa d to t he O U T PU T connecto r and
a dj ust t he A MPL co n trol for t h e desired outp ut am p litu de .
V a r iable DC Offset
Pull outwar d on t he
O
FF
S E T
con
trol (pull switc h a dded
at S N 13020000) to positio
n t h edo level (baseli n e) of t h e
outpu
t waveform . F or exam p le, +5 V of offset will i n c r ease
t
he
do
+ p eak ac voltage of α7 .5 Vρ
- ρ
out p ut to +5 and
+12 .5 V do + p ea k ac w h ile -5 V of offset will re d uce t h e
d o + pda k ac outp ut to +2 .5 V a nd -5 V .
REV . C JUL 197 8
O PER ATIO N
Ope r ati n g I n st ru ctio n s- F G 501
Gate d ( B urst)
Output
an
d V ariable Ph ase
Α gating sig n al of 2 to 15 V amplitu d e a pp lie d to t he
GAT E I NPU T connector wit h t h e PHAS E control pu lled
out will provide α burst of cycles at t he O U T PU T
co nn ector . T he d uration of t h e burst a nd nu mber of cycles
in t h e bu r st depen d on t h e gati ng signal du r atio n an d t he
output fre q uen cy selecte d . Wh en t h e gati
ng sig n al goes to
t h e zero level, t he ge
n
erator
completes its last cycle an d
remains q uiescent
un til t h e n ext gating signal .
Si ngle cycles can b e obtained by a p plyi
ng
α
gati ng
signal
wit h α perio d approximately equal to t
he
p erio
d of
t
he F G 501 ou tput waveform . T he n um b er of
cycles pe r
b urst can be ap p roximated by d ivi d i n g
t he gating sig n al
duration by t he p eriod of t h e
F
G
501 out p ut f r eq ue ncy .
GAT
E INPU T
OUT PU T
GAT E INPU T
OUTPUT
GAT E
I NPU T
OUTPUT
PH AS
E co n tr ol
at
90 ° L AG
PH AS E co n trol at
0 °
PHAS E co n tr ol at 90 ° LE AD
1431-04
F ig . 1-6 . Si n gle
cycle ou tp u t wit h variable ph ase .